A chain saw driven by a compact engine, such as a two-stroke cycle engine, is widely used as a tool for cutting tree trunks, branches and the like. Usually, a worker works in a state in which he holds a chain saw. More particularly, sometimes, a worker prunes overhead tree-branches or climbs up a tree to work. Accordingly, it is important that a chain saw is light and compact so that a worker can easily lift up the chain saw with one hand. In order to miniaturize a chain saw, the arrangement of an engine body, an exhaust pipe, a saw chain portion, and the like, and the mounting thereof in a housing are devised (see JP-S61-160201-A).
In a recent chain saw, an engine body is accommodated in a housing formed integrally therewith. A saw chain portion and the like are attached thereto via the housing. However, in order to reduce in weight, the housing is made of plastics. Thus, the housing made of plastics is inferior in stiffness and strength of the material thereof to a housing made of metal. Consequently, it is necessary to devise the design and the manufacture of the chain saw.